Hydraulic forming attachment for presses



Nov. 25, 1958 OL R 2,861,531

HYDRAULIC FORMING ATTACHMENT FOR PRESSES Filed July 10, 1956 2Sheets-Sheet 1 Nov. 25, 1958 H, MQLLER 2,861,531

' HYDRAULIC FORMING ATTACHMENT FOR PRESSES Filed July 10, 1956 2Sheets-Sheet 2 d mdw /zw Unite States HYDRAULIC FORMING ATTACHMENT FORPRESSES F Hugo Miiller, Trollhattan, Sweden, assignor to Svenskaiaeroplan Aktiebolaget, Linkoping, Sweden, 21 corporatron of SwedenApplication July 10, 1956, Serial No, 596,992 3 Claims. c1. 113-44 Thisinvention relates to the art of forming sheet metal blanks into a widevariety of dished or cupped objects by means of hydraulic pressureapplied to the blank through an elastic wall, and it is thus closelyrelated to the invention disclosed in the copending application of HugoMoller, Serial No. 473,926, filed December 8, 1954, now Patent No.2,761,405.

Presses especially designed to utilize this method of shaping andforming sheet metal blanks are not new to the art, but a pressspecifically designed for this purpose is not only expensive, butlimited in its use.

As in the aforesaid copending application of Hugo Mtiller, it is aprimary object of this invention, therefore, to provide a device whichmay be readily installed in a conventional press to convert the same tothe forming of sheet metal blanks by hydraulic pressure applied to theblank through an elastic or conformable Wall.

In the device of the aforesaid copending application, the elastic wallwas positioned across the mouth of a bore opening to the bottom of abody member, overlying the die cavity in which the blank was to beformed. Hydraulic pressure was exerted on a blank placed in the diethrough said elastic wall by the descent of a plunger in the body boreas a consequence of closure of the press. According to the aforesaidcopending application, however, the plunger was forced downwardly by thepress into a liquid filled receptacle defined jointly by the bottom ofthe plunger itself, the wall of the bore inwardly of the mouth thereof,and the elastic wall closing the mouth of the bore.

With this construction, the operativeness of the device depended to alarge degree upon the provision of exceptionally good fluid-tight sealsbetween the plunger and the wall of the bore in which it reciprocated,and also between the elastic wall and the wall of the bore in the bodymember. Obviously, the provision of highly effective sealing means in adevice of the character described was not only expensive, but thepresence of such seals represented a potential source of trouble.

It is a purpose of the present invention, therefore, to provide a deviceof the character described wherein hydraulic forming pressure is appliedto a blank in a die cavity as a consequence of descent of a plungerduring closure of the press, but wherein the plunger acts upon aliquid-filled entirely closed sack, an exposed bottom wall of whichbears against the blank to exert formingvpressure thereon. The provisionof a closed elastic liquid-filled sack in a device of the characterdescribed is highly advantageous since it obviates the need foremploying complicated and troublesome seals between the plunger and thewall of the bore in which it operates, and between the wall of the borein the body member and the conformable or elastic wall across the mouththereof.

More specifically, it is a purpose of this invention to provide a deviceof the character described incorporating a closed liquid-filled elasticsack which is adapted to be acted upon by a plunger as a consequence ofclosure of apron, and wherein the sack is-mountecl in the bore of2,861,531 Patented Nov. 25, ,9 3

Still another purpose of this invention resides in the provision of adevice of the character described which incorporates a liquid-filledelastic sack having a removable closure, and wherein the plungercooperates with the closure for the sack during the pressure stroke ofthe plunger to effect sealing of the sack with an effectiveness whichincreases in proportion to the increase in the pressure of liquid in thesack.

In this respect, it is a more specific purpose of this invention toprovide a device of the character described wherein the plunger has awell in its bottom of a size and depth to receive a filler neck on thetop wall of the sack when the plunger descends onto the sack, andwherein the closure for the sack has a tubular shank portion fitting insaid neck to be expanded by the pressure of liquid in the sack in thepower stroke of the plunger to effect sealing of the neck with a fluidtight joint which increases in effectiveness in proportion to theincrease in the pressure of liquid in the sack.

With the above and other objects in view, which will appear as thedescription proceeds, this invention resides in the novel method andconstruction, combination and arrangement of parts substantially ashereinafter described and more particularly defined by the appendedclaims, it being understood that such changes in the precise embodimentof the hereindisclosed invention may be made as come within the scope ofthe claims.

The accompanying drawings illustrate one complete example of thephysical embodiment of the invention constructed according to the bestmode so far devised for the practical application of the principlesthereof, and in which:

Figure 1 is a perspective view partly in section, illustrating thedevice of this invention mounted in a conventional doubleacting press,the press being shown open; and

Figure 2 is a view similar to Figure l, but illustrating the position ofthe parts when the press is closed.

Referring now to the accompanyingdrawings in which like referencecharacters have been applied to like parts in the two views, the numeral5 designates the table of a conventional double-acting press having apair'of press heads 6 and 7 which may be moved downwardly toward thetable 5 either simultaneously or consecutively. Since the press headoperating means forms no part of this invention, it has not beenillustrated.

The adaptor device of this invention may be said to comprise three maincomponents, a die holder 8, a body member 9 and a plunger 10. The dieholder is adapted to seat fiatwise upon the press table 5 to which itmay be adjustably anchored as by a series of dogs 11. As shown, the dieholder is in the form of a ring or annulus having a flat top surface 12parallel to the surface of the table 5, and a cylindrical bore 13 toreceive a die 14.

The die, of course, may be held by the die holder 8 in any desiredposition beneath the press heads, and it has an annular top wall 15which is preferably fiat and flush with the top wall 12 of the dieholder. The cavity 16in the die opens upwardly at the top of the die,inwardly of its annular top wall 15.

The body member 9 of the adaptor device of this invention is readilyremovably secured to the underside of the outer press head 6, directlyover the die holder, by a series of screws 18 spaced from one anotheraround the edge of a hole 19 in the bottom of the head 6. The mainportion of the body member 9 comprises a cylindrical block of metalhaving an upwardly facingannular shoul- 4 der 21 engaging theunderside'of the outer'press 'head'6 around the edge of the hole 19therein, and into which the screws 18 are threaded soas to securely'holdthe body member in position upon the outer press head. The body memberalso has a flat bottom face 22 parallel to the shoulder 21 and of a sizeto overlie the top surfaces 12 and of the die holder and the die14therein.

At its upper portion, the body member 9 has a coaxial neck 24 of reduceddiameter which projects upwardly through the hole 19 in the bottom ofthe press head, in spaced concentric relation thereto, and a verticalbore 25 extends axially through the neck and into the larger diameterlower portion of the body 9 to communicate with a counterbore 26 in thelower portion of the body member. The counterbore 26 opens totheunderside of the body member and provides a compartment in the lower endportion of the body member in which the closed liquid-filled elasticsack 27 of this invention is mounted.

The elastic sack 27 is preferably made of substantially heavy rubberalthough it will be understood that any other material having theflexible and elastic characteristics of rubber may be employed. As seenbest in Figure 1, the sack has a substantially flat circular bottom wall28, a cylindrical side Wall 29 integrally joined to the peripheralportion of the bottom wall and a substantially flat top wall 30integrally joined at its periphery with the upper end of the side wall.Projecting upwardly from the center of'the top wall and integraltherewith is a tubular neck 31 closed by a removable plug 32, and whichprovides for filling the sack with liquid 33.

As will appear at greater length hereinafter, the plug 32 has adisc-like top portion 34 which overlies the upper end of the neck 31 anda tubular shank portion 35 which is received within the neck 31 with asnug lit and opens to the interior of the sack. The lower end of theshank portion of the plug is preferably provided with an outwardlydirected annular flange 36 which engages under the top wall 30 at itsjunction with the neck. It is important to note that the plug 32 islikewise made of a resilient or elastic material such as rubber.

As seen best in Figure 1, the cylindrical side wall 27 of the sack has adiameter to snugly fit the wall of the counterbore 26, and the length ofthe sack is such that its top wall 30 seats against the downwardlyfacing shoulder 38 provided by the bottom of the counterbore 26 in thebody member, while the bottom wall 28 of the sack extends across themouth of the counterbore to normally lie in a plane either flush withthe underside of the body member or spaced slightly above its underside.

The sack is removably retained in the counterbore 26 by means of acircumferential bead 40 on its side wall, intermediate the axial ends ofthe sack, snugly received in and fitting a circumferential groove 41 inthe wall of the counterbore.

The plunger 10 preferably, though not necessarily, has a close slidingfit in the bore 25 in the body member. It projects upwardly through thehole 19 in the underside of the press head 6 and is normally supportedin an elevated position on the body member by means of a helical spring43 loosely encircling the neck 24 on the upper end of the body memberand confined axially between the upwardly facing shoulder 21 on the bodymember and an enlarged head 44 on the upper end of the plunger. Thespring 43 thus levitates the plunger so that when the press is open theliquid-filled sack 27 is relieved of the weight of the plunger. In thisposition of theparts, the enlarged head 44 on the top of the plunger isalso spaced somewhat from the bottom of the inner press head or ram 7.

As seen best in Figure 1, the lower end of the plunger 10 has adownwardly opening well 46 formed therein of a diameter to freelyslidingly receive the neck 31 and the plug therein upon descent of theplunger. The depth of the well 46 is also substantially equal to theheight of the neck 31 plus the head of the plug therein so that when theplunger is forced downwardly by the inner press head 7, the plugged neckof the liquid-filled sack will engage the bottom of the well 46 in theplunger substantially at the same time that the portions of the plungersurrounding the well engage the top wall 30 of the liquidfilled sack.

Although Figure I shows the plunger fully disengaged from the neck 31and spaced a substantial distance above the topwall 30 of the liquidfilled sack, these parts have been so illustrated merely for the sake ofclarity. In actual practice the plunger does not leave the top wall ofthe sack when the press opens, so that there is no problem of airpockets between the plunger and the sack, and no need for venting suchpockets, which would be the case if the spring 43 lifted the plungerentirely off of the liquid filled sack.

With the construction described, it will be seen that whenever downwardpressure is exerted upon the top wall 30 of the liquid-filled sack bythe plunger during closure of the press in the manner illustrated inFigure 2, the increasing pressure of liquid in the sack is manifested inthe hollow shank portion 35 of the plug 32 so as to tend to radiallyexpand the shank portion of the plug and thus tightly engage its outersurface with the inner surface of the neck 31 on the sack. At the sametime, the neck 31 is tightly clamped between the shank portion of theplug and the wall of the well in the underside of the plunger. In thisway, the elastic sack is closed by a seal, the effectiveness of whichincreases in proportion to the build-up of pressure of liquid in thesack as the plunger descends during closure of the press.

It will also be observed that rubbing friction between the sack and thewalls of the chamber in the lower portion of the body member issubstantially eliminated with the result that there is practically nowear upon the sack itself at its areas which lie contiguous to the bodymember. Only the lower end portion or face of the plunger contacts thatportion of the top wall 30 of the sack which lies between the centrallydisposed neck 31 and the bore 25 in which the plunger operates, andduring the descent of the plunger, while it is possible that the topwall of the sack may be deformed around the exterior of the lower end ofthe plunger, such deformation takes place with a folding in actionpractically entirely without rubbing friction.

' If the bottom wall 28 of the elastic sack is spaced a slight distanceabove the bottom 22 of the body member, as shown, the slight space whichresults may be employed to accommodate a wear disc 48 of rubber or othersimilar elastic material, it being understood that the wear disc is of asize to overlie the entire underside of the bottom wall 28 of the sack.The wear disc may be removably secured in position flatwise engaging theunderside of the bottom wall 28 on the sack as by having its peripheraledge portions snapped into a circumferential groove 49 in the bottomportion of the body member directly adjacent to the mouth of thecounterbore 26 therein.

Except for the fact that the bottom of the plunger 10 bears directlyupon a closed liquid-filled sack in the compartment provided by thecounterbore 26 in the bottom portion of the body member, the operationof the adaptor device of this invention is substantially the same asthat in the aforesaid copending application of Hugo Mtiller, Serial No.473,926, filed December 8, 1954, now Patent No. 2,761,405. Assuming thatthe parts have been set up in the manner described and that the press isopen, the body member 9 will occupy a raised position a substantialdistance above the top of the die holder and the die 14 therein. Withthe press open, the metal blank to be formed in the die is placed on topof the die with its upper portions resting upon the flat upper face 12of the die holder. Thereafter, an annular pres sure plate or washer S1is laid on top of those portions of the blank which overlie the upperfaces 12 and 15 of the die holder 8 and die 14, respectively. This plateor washer may be formed of a suitable hard Wood or other similarmaterial, and its central aperture is preferably slightly larger thanthe mouth of the cavity 16 in the die. If desired, a second wear disc48' similar to the wear disc 48 but of a size to be received in thecentral hole of the pressure plate 51, may be placed upon the blankinside the plate 51. Such a second disk 48' is especially useful wherethe depth of the cavity to be formed is deeper than it is practicable toform in one operation, in which event the disk 48 is of a size to fillthe cavity in the blank resulting from the first pressing operation.This avoids unnecessary strain upon the wear disk 48 and the sack 27and, of course, eliminates possible entrapment of air during the secondpressing operation.

With the parts thus positioned, the outer press head 6 may then belowered to bring the underside 22 of the body member down onto thepressure plate 51 to effect clamping of the blank between it and the topof the die and die holder, with a force sufficient to prevent wrinklingof the blank as it is drawn inward during the forming operation. Whilethe outer press head 6 is maintained in its lowered position thusexerting clamping pressure upon the work, the inner press head or ram 7is lowered to force the plunger 10 down onto the top wall 30 of theliquid-filled flexible sack 27. As will be readily apparent, the closureof the inner press head 7 and resulting descent of the plunger 10 uponthe liquid-filled sack acts hydraulically on and through the elasticbottom wall 28 of the sack and the wear discs 48 and 48' underlying thesame to cause them to exert downward pressure on the blank, to thusforce it into the die cavity and deform the blank to the shape of thecavity.

After the forming operation, the press is opened and the formed part maybe quickly dislodged from the die by air pressure acting against theunderside of the deformed part. For this purpose, both the die and thedie holder are provided with radial passages 53 and 54, respectively,which register with one another. The inner passage 53 in the diecommunicates with a small diameter bore 55 opening upwardly into the diecavity 16, while the outer passage 54 in the die holder is connectiblewith an air supply line 56 by which air under pressure may be introducedinto the die cavity beneath the deformed part therein after the pressingoperation.

From the foregoing description, taken together with the accompanyingdrawings, it will be readily apparent to those skilled in the art thatthis invention provides an improved, but simple and highly effectivedevice for quickly and easily adapting any ordinary press to theformation of sheet metal blanks by means of hydraulic pressure actingthrough an elastic or conformable wall, which elastic wall is formed aspart of a closed liquidfilled sack and thus requires no complicated orcostly sealing means for the plunger as was previously required indevices of this type.

What is claimed as my invention is:

1. In a device of the type wherein pressure is exerted upon a blank toform the same in a die upon which the blank is supported as aconsequence of pressure produced downward motion of a plunger toward theblank: a body member having a vertical bore therethrough, the upperportion of which is smaller in diameter than its lower portion toprovide a cylinder, the plunger being reciprocably mounted in saidcylinder to enter the larger diameter lower portion of the bore as itdescends; an elastic, liquid-filled sack mounted in the larger diameterlower portion of the bore so as to be interposed between the bottom ofthe plunger and the blank to be formed, said sack having a top walllarger in diameter than the cylinder and having a bottom wall extendingacross the mouth of the bore and through which the pressure resultingfrom descent of the plunger upon the sack is hydraulically applied to ablank in place beneath the sack, said sack being imperforate except fora tubular neck which extends from its top Wall toward the plunger, inspaced concentric relation to the wall of the cylinder, said neckproviding an inlet for the sack; a plug closing said sack inlet, saidplug having a tubular shank portion of elastic material fitting in saidneck with its exterior surface in intimate engagement with the innerwall surfaces of the neck, the interior of said tubular neck being inopen communication with the interior of the sack so that said shankportion tends to expand in the neck as a consequence of the rise inpressure in the sack which results from the exertion of blank formingpressure on the blank by the sack; and said plunger having a well in itsunderside of a size and shape to accommodate the neck and its plug whenthe plunger descends upon the sack so as to prevent expansion of theneck under the expansive force exerted thereon by the shank portion ofthe plug and to assure seal ing of the neck by the plug with a forcewhich increases in proportion to the build up in liquid pressure in thesack.

2. The device set forth in claim 1, wherein said plug has a disc at itsupper end engaging over the upper end of the neck on the sack, and hasan outwardly directed annular flange on the inner end of its shankportion which engages under the lower end of the neck at the junction ofthe latter with the sack to prevent accidental displacement of the plugfrom the neck.

3. In a device for shaping a sheet metal block to the configuration of adie by forcing the blank into the die by means of hydraulic pressureapplied to the blank through an elastic wall: a body member having avertical bore in its upper portion to provide a cylinder and having acounterbore in its lower portion connecting with the cylinder andopening to the bottom of the body, the junction between the bore and thecounterbore forming an abrupt downwardly facing surface; a plungerreciprocable in the cylinder and adapted upon descent thereof to enterthe counterbore; an elastic liquid filled closed sack in andsubstantially filling the counterbore, said sack having a cylindricalside wall snugly engaging the side of the counterbore, a bottom wallwhich extends across the mouth of the counterbore to bear against theblank to be shaped, and a top wall which in the free condition of thesack has its peripheral portion bearing against said downwardly facingsurface which forms the junction between the cylinder and the counterbore while its medial portion extends across the bottom of the cylinderto have the underside of the plunger engage the same and apply pressurethereon as the plunger descends into the counterbore; and interengagingmeans on the side wall of the sack and the side of the counterbore toconstrain the sack against sliding axially in the counterbore.

References Cited in the file of this patent UNITED STATES PATENTS731,367 Huber June 16, 1903

